Supporting device for an abrasive tool and corresponding abrasive tool

ABSTRACT

A supporting device ( 1 ) is described for supporting and containing an abrasive element ( 5 ) for the machining of stone, ceramic or similar, said supporting device ( 1 ) comprising an elastic means ( 6 ) for absorbing the external stress on said abrasive element ( 5 ); said supporting device ( 1 ) comprises an upper half-box ( 3   b ) and a lower half-box ( 3   a ) which comprise reciprocal engagement means ( 7 ), thus forming a housing box ( 3 ) able to accommodate said elastic means ( 6 ) and able to retain said abrasive element ( 5 ), said reciprocal engagement means ( 7 ) being suitable for permitting the sliding of said upper half-box ( 3 b) towards and away from said lower half-box ( 3   a ). 
     An abrasive tool ( 2 ) is also described for machining stone or similar, comprising an abrasive element ( 5 ) and a supporting device ( 1 ) for supporting and containing said abrasive element ( 5 ).

DESCRIPTION

The present invention relates to a supporting device for an abrasive tool and a corresponding abrasive tool.

As is known, abrasive surface machining, for example lapping, polishing or grinding of stone, marble, ceramic, vitreous material etc. requires the use of abrasive tools, which are brought into contact with and pressed against the surface to be machined. Said abrasive tools are normally supported by a head for abrasive tools, which is a machine able to force relative movements between the material to be machined and the abrasive tools, and to perform the necessary compression of said abrasive tools on said surface to be machined, so as to allow the surface machining to be carried out.

In particular, a head for abrasive tools is known applied to a conveyor belt which conveys the material to be machined along a substantially horizontal path. Said head for abrasive tools supports a plurality of abrasive tools, arranged so as to define the vertexes of a plurality of polygons; said abrasive tools are brought into contact with and pressed against the material to be machined and, at the same time, are forced to perform both a first rotatory movement around a vertical axis, in the centre of each of said polygons, so that the abrasive tools are brought into contact with the entire surface to be machined, and a second rotatory movement around a horizontal axis in a raised position (as in a pendulum) to ensure uniform wear on the abrasive layer; said second rotatory movement is forced by second motor means.

In a head of this type for abrasive tools, abrasive tools that comprise an abrasive layer and a supporting device are normally used.

Said abrasive layer is suitable for being brought into contact with and pressed against the material to be machined. Normally, said abrasive layer is a diamond wheel which comprises fragments of diamond incorporated in a mass of resin-like material. Said abrasive layer normally has a protuberant form with a first lateral edge, a second lateral edge and a contact surface defined by said first and second lateral edge.

Said supporting device normally comprises:

-   -   a supporting layer, which sustains the abrasive layer; said         supporting layer, which is normally made of rigid plastic         material, is in turn supported by the above-mentioned head for         abrasive tools;     -   an elastic layer, positioned between said abrasive layer and         said supporting layer, able to absorb the stress on the abrasive         tool; normally, said abrasive layer is formed of a cushion made         of rubbery, natural or synthetic material.

Normally, the elastic layer is glued, on a first face, to the supporting layer and, on a second face, to the abrasive layer to form a sandwich structure. The adhesive used is normally cyanoacrylate.

During machining, the above-mentioned second rotatory movement forces a brushing over the entire contact surface so that the supporting layer “swings”, alternately coming into contact with the first lateral edge and the second lateral edge.

The adhesive used to glue the elastic layer to the supporting layer and to glue the abrasive layer to the elastic layer of the supporting device represents an element of rigidity which tends to reduce the elasticity due to use of the elastic layer. To remedy this phenomenon, the thickness of the elastic layer would have to be increased, but this tends to produce undesired secondary effects, for example, as a result of the above-mentioned second rotatory movement due to the head for abrasive tools, the above-mentioned supporting layer tends to jam against a lateral edge thus forcing the elastic layer to bend and preventing the contact surface coming into contact with the surface to be machined, resulting in non-uniform abrasion and wear of the abrasive layer.

Furthermore, cyanoacrylate is a substance with toxic properties during both production and disposal of the abrasive tool, consequently the use of said substance should be avoided or at least limited.

In addition, it has been seen experimentally that, during the machining phases, the phase of gluing the elastic layer on the supporting layer and the phase of gluing the abrasive layer on the elastic layer of the supporting device are critical phases, since a very high centring precision is required: if, for example, the abrasive layer is inaccurately centred with respect to the elastic layer of the supporting device, then during the above-mentioned second rotatory movement, the abrasive layer may come into contact with the surface to be machined in a dissymmetric manner, involving the risk of non-uniform abrasion of the surface to be machined.

Furthermore, the abrasive layer, which is normally the layer subject to greatest wear, adheres to the supporting device and can only be separated by lengthy and unhealthy ungluing procedures; therefore, in the event of wear of the abrasive layer only, the supporting device cannot be re-used and must consequently be disposed of, thus incurring considerable expense.

To remedy the above drawbacks, the ideal solution would be to use abrasive tools without adhesive.

Solutions which avoid the use of adhesive are known.

EP 1721702 B1 relates to an abrasive tool comprising an anchoring element able to support a body made of abrasive material comprising a particle load made of abrasive material dispersed in a mass of elastomeric material. Such a solution, although not using adhesive, is relative to a different type of abrasive tool with respect to the present invention, since the present invention concerns an abrasive tool in which the elastic layer is differentiated from the abrasive layer, contrary to said earlier invention which comprises one single layer which is both abrasive and elastic. Furthermore, said earlier invention suffers from the same drawbacks as those described above concerning the excessive length of the elastic layer, with possible jamming of the lateral edges of the abrasion surface.

GB 1065198 also uses adhesive.

The object of the present invention is to permit the production of an abrasive tool with the elastic layer separate from the abrasive layer but without using adhesive, or using it in a minimum quantity.

According to the invention, said object is achieved by means of a supporting device for supporting and containing an abrasive layer for the machining of stone, ceramic or similar, said supporting device comprising an elastic means for absorbing the external stress on said abrasive layer and characterised in that it comprises an upper half-box and a lower half-box which comprise reciprocal engagement means, thus forming a box able to house said elastic means and retain said abrasive layer, said reciprocal engagement means being suitable for allowing said upper half-box to slide near to and away from said lower half-box.

Preferably, said supporting device is such that said reciprocal engagement means comprise at least one tab integral with said upper half-box, said at least one tab snap-engaging in a respective cavity of said lower half-box.

Preferably, said at least one tab comprises a locking tooth which can be hooked to said respective cavity so as to permit said snap-engagement of said tab in said respective cavity.

Preferably, said snap-engagement is such as to allow said upper half-box to move away from said lower half-box as far as a stroke end determined by the interference of said locking tooth with the walls of said cavity, and allow said upper half-box to move towards said lower half-box with compression of said elastic means.

Preferably, the elastic means is interlocked with the upper half-box, so that a compression of said elastic means results in a shifting of said upper half-box towards said lower half-box.

Preferably, said locking tooth faces towards the outside, said respective cavity being a through cavity.

Preferably, said supporting device for said elastic means comprises a pair of elastic elements with complementary shape.

Preferably, each of said elastic elements features an alternation of solid-hollow shapes, which can be reciprocally coupled, in particular with protuberances having trapezoidal section.

Preferably, said supporting device is made of plastic.

The object of the present invention is furthermore achieved by means of an abrasive tool for the machining of stone, ceramic or similar, comprising an abrasive layer and a supporting device for supporting and containing said abrasive layer, in which said supporting device is of the type according to the present invention.

Preferably, said abrasive element has a base in the form of a sheet positioned in contact with said elastic means and retained by said upper half-box and furthermore has contact protuberances which protrude from said box.

Further characteristics and advantages of the present invention will become clearer from the description of preferred but not exclusive embodiments thereof, illustrated by way of example in the accompanying drawings, in which:

FIG. 1 shows an abrasive tool according to the present invention;

FIG. 2 shows a component of the abrasive tool of FIG. 1;

FIG. 3 shows a further component of the abrasive tool of FIG. 1;

FIG. 4 shows a further component of the abrasive tool of FIG. 1;

FIG. 5 shows a further component of the abrasive tool of FIG. 1;

FIG. 6 shows the reciprocal arrangement between the components of FIGS. 4 and 5;

FIG. 7 shows a further component of the abrasive tool of FIG. 1.

With reference to the accompanying figures, 2 indicates overall an abrasive tool according to the present invention for the surface machining of ceramic.

The abrasive tool 2 comprises a supporting device 1 and an abrasive element 5.

Said abrasive element 5 consists of a material formed of a mass of resin-like material and a percentage of fragments of diamond (in other embodiments, another type of abrasive could be used), according to ratios known per se.

Said abrasive element 5 has a base in the form of a sheet 51 retained by said supporting device 1; furthermore, said abrasive element 5 has contact protuberances 52 which protrude from said supporting device 1, alternating with spaces 55. The contact protuberances 52 have, on their respective tops, contact surfaces 53 suitable for coming into contact with and pressing against, during machining, a ceramic surface to be machined (in other embodiments, another type of material could be used, for example stone, marble or other), thus defining an overall contact surface of the abrasive layer formed of a plurality of contact surfaces 53 of each of said contact protuberances 52 between lateral edges 54 a, 54 b.

The supporting device 1 is able to support and contain said abrasive element 5.

Said supporting device 1 comprises an upper half-box 3 b and a lower half-box 3 a; said half-boxes 3 a, 3 b comprise reciprocal engagement means 7 which permit the reciprocal connection of said half-boxes 3 a, 3 b thus forming a housing box 3 able to retain said abrasive element 5. Said lower half-box 3 a is formed of a base 31 a and lateral walls 32 a positioned at the edges of said base 31 a; base 31 a and lateral walls 32 a are mutually perpendicular; in the connection area between base 31 a and lateral walls 32 a, reinforcing ribs 33 a are provided alternating with through cavities 73; said reinforcing ribs 33 a have wall-shaped ends 34 a which are a continuation of the walls of the above-mentioned cavities 73.

Said upper half-box 3 b comprises a wall-type outer edge 74, of a shape which can be substantially inserted by means of elastic locking system inside the above-mentioned lateral walls 32 a of said lower half-box 3 a. Between opposite walls, connection segments 31 b are provided joining said opposite walls, thus substantially forming a mesh structure 32 b. Said meshes 32 b, in the present embodiment, are rectangular-shaped and can be fitted into the spaces 55 of the abrasive element 5, so that the contact protuberances 52 protrude.

Said upper half-box 3 b incorporates a plurality of tabs 71 which protrude from said walls 74 substantially extending said walls 74; each of said tabs 71 terminates in a locking tooth 72, protruding towards the outside.

Advantageously, each of said tabs 71 is positioned at the level of a respective cavity 73 of said lower half-box 3 a and can be inserted inside said respective cavity 73, in a guided manner due to the effect of the ends 34 a of said reinforcing ribs 33 a. The insertion of said tabs 71 inside said cavities 73 entails an elastic flexion of said tabs 71, due to the effect of the locking teeth 72 protruding towards the outside and in sliding contact with the walls 32 a, until the locking teeth 72 go beyond said cavity 73, hooking to said cavities 73 and snap-engaging between said half-boxes 3 a, 3 b.

Said tabs 71, said locking teeth 72 and said locking cavities 73 are therefore reciprocal engagement means, indicated overall by 7.

Advantageously, said reciprocal engagement means 7 are furthermore able to permit sliding of said upper half-box 3 b towards and away from said lower half-box 3 a.

Advantageously, said snap engagement is such as to permit:

-   -   movement of said upper half-box 3 b away from said lower         half-box 3 a as far as a stroke end determined by the         interference of said locking tooth 72 with the walls of said         cavity 73;     -   movement of said upper half-box 3 b towards said lower half-box         3 a.

It should be noted that said upper half-box 3 b comprises slots 100 obtained on said walls 74. The supporting device 1 comprises an elastic means 6 made of natural rubber, shaped so that it can be inserted inside said lower half-box 3 a. Said elastic means 6 is able to absorb the external stress on said abrasive element 5 during the surface machining of the ceramic. Advantageously, the elastic means 6 comprises a pair of elastic elements 6 a, 6 b with complementary shape; in particular, each of said elastic elements 6 a, 6 b features an alternation of solid-hollow shapes, with trapezoidal section protuberances 61 a, 61 b which can be reciprocally overlapped. The top 61 a of said protuberance 6 a has surface grooves, not illustrated in the figures, able to modify the elastic properties of the elastic means 6. Furthermore, the elements of said pair of elastic elements 6 a, 6 b are made of different material.

Advantageously, the elastic element 6 b comprises interlocking elements 101 which can be coupled to said slots 100 of said upper half-box 3 b, thus resulting in interlocking between said elastic means 6 and said upper half-box 3 b.

Advantageously, the abrasive tool is inserted so that the base in the form of a sheet is in contact with said elastic means 6 and retained by said upper half-box 3 b once said upper half-box is closed on said lower half-box.

Once the above-mentioned components have been obtained, the abrasive tool 2 is produced as follows:

-   -   housing of the abrasive element 5 inside said upper half-box 3         b;     -   interlocking between said elastic means 6 and said upper         half-box 3 b with interlocking between said slots 100 and said         interlocking elements 101 and simultaneous juxtaposition of said         elastic means 6 with said abrasive element 5;     -   interlocking between said lower half-box 3 a and said upper         half-box 3 b by insertion of said tabs 73 until said locking         teeth 72 hook in said cavities 73.

At this point, the abrasive tool 2 is complete and can be mounted on a head for abrasive tools, from which said abrasive tool 2 can be used for surface machining of the ceramic.

At rest, i.e. when the abrasive element 5 is not in contact with and pressing against the surface to be machined, the abrasive tool 2 is in said stroke end position in which each locking tooth 72 is hooked to the respective cavity 73.

Advantageously, during machining, i.e. when the abrasive element 5 is in contact with and pressing against the surface to be machined, the abrasive tool 2 is able to absorb stress acting on said abrasive element 5. In fact, when the abrasive element 5 is pushed towards said lower half-box 3 a, the following phenomena occur:

-   -   said elastic means 6 is compressed;     -   for interlocking between the slots 100 of the upper half-box 3 b         and the interlocking elements 101 of the elastic element 6 b,         said upper half-box 3 b is pushed towards said lower half-box 3         a.

Both said phenomena act so as to allow said abrasive element 5 to move towards said lower half-box 3 a.

When the stress on said abrasive element 5 ceases, said elastic means 6 pushes said upper half-box 3 b which is thus re-set to the stroke end position.

It can be noted that, advantageously, the movement of said upper half-box 3 b substitutes an analogous compression of the elastic means 6, which can therefore be thinner than an elastic layer according to the known art.

Not only is there no adhesive, but a supporting device is also obtained which potentially uses less rubber or uses the same quantity of rubber as the known art but has improved absorbing properties.

Furthermore it can be noted that according to the present invention the supporting device is a device separate from the abrasive element; this allows not only the separate sale of said two products but also simple re-use of the supporting device when the abrasive element is worn. 

1. Supporting device for supporting and containing an abrasive element for the machining of stone, ceramic or similar, said supporting device comprising an elastic means for absorbing the external stress on said abrasive element and characterised in that it comprises an upper half-box and a lower half-box which comprise reciprocal engagement means, thus forming a housing box able to accommodate said elastic means and able to retain said abrasive element, said reciprocal engagement means being suitable for permitting the sliding of said upper half-box towards and away from said lower half-box.
 2. Supporting device as claimed in claim 1, wherein said reciprocal engagement means comprise at least one tab integral with said upper half-box, said at least one tab being snap-engageable in a respective cavity of said lower half-box.
 3. Supporting device as claimed in claim 2, wherein said at least one tab comprises a locking tooth hookable to said respective cavity in order to permit said snap engagement of said tab in said respective cavity.
 4. Supporting device as claimed in claim 3, wherein said snap engagement is such as to permit: movement of said upper half-box away from said lower half-box as far as a stroke end determined by the interference of said locking tooth with the walls of said cavity; movement of said upper half-box towards said lower half-box with compression of said elastic means, said elastic means being interlocked with said upper half-box.
 5. Supporting device as claimed in claim 4, wherein said locking tooth faces outwards, said respective cavity being a through cavity.
 6. Supporting device as claimed in claim 1, wherein said elastic means comprises a pair of elastic elements with complementary shape.
 7. Supporting device as claimed in claim 6, wherein each of said elastic elements features an alternation of solid-hollow shapes, reciprocally couplable, in particular with protuberances having trapezoidal section.
 8. Supporting device as claimed in claim 7, wherein the elastic elements of said pair of elastic elements are made of different material.
 9. Supporting device as claimed in claim 1, wherein said supporting device is made of plastic.
 10. Abrasive tool for machining stone or similar, comprising an abrasive element and a supporting device for supporting and containing said abrasive element, wherein said supporting device is as claimed in claim
 1. 11. Abrasive tool as claimed in claim 10, wherein said abrasive element has a base in the form of a sheet positioned in contact with said elastic means and retained by said upper half-box and also features contact protuberances which protrude from said housing box.
 12. Supporting device as claimed in claim 2, wherein said elastic means comprises a pair of elastic elements with complementary shape.
 13. Supporting device as claimed in claim 3, wherein said elastic means comprises a pair of elastic elements with complementary shape.
 14. Supporting device as claimed in claim 4, wherein said elastic means comprises a pair of elastic elements with complementary shape.
 15. Supporting device as claimed in claim 5, wherein said elastic means comprises a pair of elastic elements with complementary shape.
 16. Supporting device as claimed in claim 2, wherein said supporting device is made of plastic.
 17. Supporting device as claimed in claim 3, wherein said supporting device is made of plastic.
 18. Supporting device as claimed in claim 4, wherein said supporting device is made of plastic.
 19. Supporting device as claimed in claim 5, wherein said supporting device is made of plastic.
 20. Supporting device as claimed in claim 6, wherein said supporting device is made of plastic. 